Fig. 1: Experimental design.

Participants with narcolepsy went through five 20-min naps during the same day. In each nap, periods with stimulation (ON) alternated, every minute, with periods when no stimulus was presented (OFF). During the ON periods, participants were presented with words and pseudo-words and asked to either frown (corrugator muscle contractions) or smile three times (zygomatic muscle contractions) in response to the stimuli. Stimuli were presented every 10 s (±1 s). Following each nap, participants were asked to report whether (1) they had any dream, (2) they were lucid and (3) they recalled any words presented during the nap. Immediately after this debriefing, participants performed a forced-choice ‘old/new’ recognition task. Healthy participants went through the exact same procedure except that they had a single 100-min nap.